I am using Garageband since a long time. I want the sound to be decreased and increased without me modifying it, on a song I recorded on GB. Is there a solution to this?

As already mentioned by Felainum1977, you should be using automation if you want to increase or decrease the level of your audio without actually modifying the audio itself.

To use automation in Garageband, press ‘A’ on your qwerty keyboard and it will show you the automation lane on each track. If you don’t want to use ‘A’ the automation lane is also accessible from the Mix menu.

You can then draw in your automation however you like using a variety of tools. During playback, the fader for the track you have been working on will follow the automation you drew in, and the volume changes made by that automation will be heard, and heard in any mix you export when you’re finally done.

I am using Garageband since a long time. I want the sound to be decreased and increased without me modifying it, on a song I recorded on GB. Is there a solution to this?

As already mentioned by Felainum1977, you should be using automation if you want to increase or decrease the level of your audio without actually modifying the audio itself.

To use automation in Garageband, press ‘A’ on your qwerty keyboard and it will show you the automation lane on each track. If you don’t want to use ‘A’ the automation lane is also accessible from the Mix menu.

You can then draw in your automation however you like using a variety of tools. During playback, the fader for the track you have been working on will follow the automation you drew in, and the volume changes made by that automation will be heard, and heard in any mix you export when you’re finally done.

The display main track option will help you to automate the process of increasing and decreasing the volume on your tracks. You can enable it in the song’s menu.

I was using Garageband on my windows with some method I found online. But that doesn’t work any longer. Do you know if there is some other way?

Thanks @Felainum1977, I will try it.
For WIndows, You can use Vmware application Or Virtual Box Application. Both are Free and Easily available on internet to download. I found this guide on internet here where steps are well explained. Cheers!

The display main track option will help you to automate the process of increasing and decreasing the volume on your tracks. You can enable it in the song’s menu.

I was using Garageband on my windows with some method I found online. But that doesn’t work any longer. Do you know if there is some other way?

Thanks @Felainum1977, I will try it.
For WIndows, You can use Vmware application Or Virtual Box Application. Both are Free and Easily available on internet to download. I found this guide on internet here where steps are well explained. Cheers!